#include<stdio.h>
#define num 10
void find(int arr[num])
{
	int count = 0;
	for (int i = 0; i < num; i++)
	{
		for (int j = 0; j < num; j++)
		{
			if (arr[i] == arr[j]) count++;
		}
		if (count == 1) printf("%d\n", arr[i]);
		count = 0;
	}
}

main()
{
	int arr[num] = { 1, 2, 3, 4, 5,6,4, 3, 2, 1 };
	find(arr);
}